Social Motor Synchrony and Rapport in Autistic, Non-Autistic, and Mixed Neurotype Dyads
In this registered report (Efthimiou et al. 2025), we explored whether:
| Group | N |
Mean Age |
SD Age |
Gender |
|---|---|---|---|---|
| Autistic | 38 | 31.4 | 8.2 | 21F, 17M |
| Non-autistic | 48 | 29.8 | 7.5 | 27F, 21M |
| Total | 86 | 30.5 | 7.9 | 48F, 38M |
Figure 1: Screenshot of the ROI in the MEA software illustrating participants’ seating positions (left/right) and coloured ROIs.
Figure 2: Distribution of SMS scores by dyad neurotype (nonautistic, mixed, and autistic). The half-violin plots display the density distribution of SMS for each group. Boxplots indicate the interquartile range and median for each group. Individual data points are coloured black, and the grey dot represents the mean SMS for each neurotype.
A one-way ANOVA (F(2, 40) = 0.09, p = .91, η² = .005) revealed no significant differences in SMS between autistic, mixed, and non-autistic neurotype dyads (H1 not supported). This contrasts with prior research suggesting lower SMS in autistic interactions and indicates that autistic individuals synchronise at similar levels to non-autistic individuals.
Figure 3: Relationship between SMS and Rapport across different neurotypes. Note. The plot shows regression lines shaded with standard error bands (ribbons) around the fitted lines for Autistic (blue), Mixed (orange), and Non-autistic (black) dyads.
A linear mixed-effects model indicated that while SMS did not overall significantly predict rapport, non-autistic dyads exhibited a significantly steeper positive relationship compared with autistic dyads (Mdiff = 4.14, SE = 1.90, t(39) = 2.176, p = .036, CI [0.29, 7.98]). This suggests that non-autistic individuals might rely more on SMS for social bonding.
A one-tailed t-test revealed that the non-autistic group (M = 0.73, SD = 0.18) had significantly higher ratio scores than the autistic group (M = 0.65, SD = .21; t(84) = 2.04, p = .022, Cohen’s d = 0.45). This finding suggest that autistic and non-autistic individuals engage in rapport-building via different mechanisms.
Our findings indicate that while autistic individuals synchronise at levels comparable to non-autistic individuals, the relationship between SMS and rapport is significantly stronger in non-autistic dyads. This suggests that social bonding in non-autistic groups is more dependent on SMS, potentially due to an over-reliance on such cues, whereas autistic individuals may rely on alternative mechanisms.